Overclocking And Core Unlocking

How To Overclock A Clarkdale

As I mentioned before, I killed the previous Pentium G6950 in an overzealous overclocking attempt. After achieving reasonable load temperatures, I recklessly applied 1.475V to the processor, which is far too much for the Clarkdale-based CPU to handle, but enough to get it to 4.5 GHz. It worked for a while, and died during testing.

A more reasonable limit is 1.375V. That is exactly what we're setting the CPU voltage to in our current Pentium G6950 overclocking attempt, and the goal is to take it as far as that voltage will allow. With CPU Vcore set to 1.375V, the CPU Vtt set to 1.37V, the PCH core set to 1.16V, and the CPU PLL set to 1.9V, we'll see what this puppy can do.

I'm going to mention that the new Pentium G6950 sample we're using is a sample we purchased from Newegg, not some cherry-picked chip coming from Intel. Nevertheless, the CPU is ever-ready to overclock. It takes no effort to get this processor to 4.5 GHz with Prime95 load temperatures under 70 degrees Celsius. Of course, we have to keep things interesting, so we once again push the hardware past the point of reason.

At 4.6 GHz, the machine boots, but quickly crashes and damages the Windows installation while doing so. After a re-install, the machine still boots at 4.5 GHz, but the mouse does not work—it is likely that the chipset has been pushed past its limits. Stability is re-established with the system clocked to 4.3 GHz. Honestly, this is more of a reasonable overclock anyway, and we don't think there's much performance lost in those 200 MHz, but it's interesting to see that both of our Pentium G69500 samples made it to 4.5 GHz.

A final 4.3 GHz clock speed with low Prime95 load temperatures is fine by us. With a 205 MHz reference clock and a 2,870 MHz QuickPath Interconnect (QPI), that's an overclock of 1.5 GHz. This is certainly nothing to sneeze at, and if that doesn't wake up this CPU, nothing will.

Since we're using the same CPU and motherboard we did in our last review, we once again set the Phenom II's voltage to 1.5V, the multiplier to 19x, and the HyperTransport reference clock to 213 MHz, yielding a final dual-core overclock of 4.065 GHz.

But there is more work to do here. Our readers mentioned that they'd like to see if this processor can be unlocked--that is to say, can our dual-core Phenom II operate successfully with its two dormant CPU cores enabled? Can it become a true quad-core CPU?

To find out, you need a motherboard that supports core unlocking. Our Asus M4A785TD-V EVO motherboard supports this feature, so all we have to do is open the BIOS settings, enable Advanced Clock Calibration (ACC), activate Unleashing Mode, and select the number of CPU cores we want to activate. After activating all four cores to see if it would work and a quick reboot, we were rewarded with four usable CPU cores. The CPU won't overclock quite as high as it does with only two cores enabled, but comes close. With the multiplier set at 18x and the HyperTransport reference clock at 213 MHz, the final quad-core overclock is 3.8 GHz. It will be interesting to see if that 200 MHz clock speed deficit matters with twice the number of processor cores activated.

Since we were successful in our unlocking endeavors, I will mention that AMD provided our CPU sample. If you're planning to buy a Phenom II X2 555 just to see if all four cores will work, you probably owe it to yourself to do a little research about the success rate. In general, I don't like to test these kind of things in a CPU comparison because there are no guarantees, and there's no way for us to tell you how to identify an unlocked chip, short of trial and error. But our readers want to see it, and if a buyer knows the risks, there's no harm done. Do consider this a fair warning, though. There is no guarantee that the Phenom II X2 555 you purchase will successfully work with all four CPU cores enabled.

With our contenders ready to rumble, let's check out the test system's specifications so we can get things moving.

notty22I don't know if this is ROFL or just sad ? Try reading the article. Your embarrassing yourself.More faulty logic by AMD fanboys. Which is it ? A budget bang for your buck rig,H55/Clarksdale=200 dollarsor890FX ($160.00 MIN)+ 555=260, all so you can buy another cpu, next year, that does not exist yet ?and 890fx, you HAVE to buy a DISCRETE graphics card now.AMD will love you , if you invest in all of this hardware , with plans to buy more, lol.

Hmmmm, talk about embarrassing yourself - didn't you even bother to find out if your numbers were right before posting? You can get a 890FX for $140, not $160 MIN as you stated. For $155 you can get one with USB 3.0 and SATA 6Gbps, and it's not implemented with the compromises inherent with the LGA 1156 platform.

You're quite incorrect about needing a discreet GPU. AMD sells the 890GX, 790GX, 785G, 760G, and 880G. In fact, the platform they used had an integrated GPU. The nice thing with the AMD platform is, they have sideport memory, so you don't degrade CPU performance when you use the IGP due to memory contention.

So, I can get the AMD platform with motherboards around $60 with an IGP, or I can get a powerful platform with two real PCI-E 16x slots, USB 3.0, and SATA 6.0 Gbps for $155. You don't have the same choices with the Pentium G6950 platform in either direction. AM3 processors have a very diverse selection of platform.

One thing to consider is the Pentium G6950 is tied to a crippled platform, whereas the Phenom II can be used with an 890FX, which has more PCI-E lanes for Crossfire, comes with SATA 6Gbps, and can have USB 3.0 added without either running degraded, or using PCI-E lanes used for the video card.

The AMD platform gives you more choices (integrated graphics, discreet graphics in several flavors, a lot of PCI lanes, or a few), and an unlocked multiplier.

One thing to consider is the Pentium G6950 is tied to a crippled platform, whereas the Phenom II can be used with an 890FX, which has more PCI-E lanes for Crossfire, comes with SATA 6Gbps, and can have USB 3.0 added without either running degraded, or using PCI-E lanes used for the video card.

The AMD platform gives you more choices (integrated graphics, discreet graphics in several flavors, a lot of PCI lanes, or a few), and an unlocked multiplier.

I dont understand they talk about the dormant cores and you may not be successful, this is a dual core shoot out, so you intended buying a dual core, why not get the phenom II 555 and see if the cores unlock if they dont well no biggie still a fast CPU but if they do BONUS, also they dont tell you that with 2 cores the phenom can easily get OVER 4GHZ, this is typical of toms not putting everything into the tests, definately Intel fans

One thing to consider is the Pentium G6950 is tied to a crippled platform, whereas the Phenom II can be used with an 890FX, which has more PCI-E lanes for Crossfire, comes with SATA 6Gbps, and can have USB 3.0 added without either running degraded, or using PCI-E lanes used for the video card.

The AMD platform gives you more choices (integrated graphics, discreet graphics in several flavors, a lot of PCI lanes, or a few), and an unlocked multiplier.

All these are important considerations.

Anonymous said:

I dont understand they talk about the dormant cores and you may not be successful, this is a dual core shoot out, so you intended buying a dual core, why not get the phenom II 555 and see if the cores unlock if they dont well no biggie still a fast CPU but if they do BONUS, also they dont tell you that with 2 cores the phenom can easily get OVER 4GHZ, this is typical of toms not putting everything into the tests, definately Intel fans

I don't know if this is ROFL or just sad ? Try reading the article. Your embarrassing yourself.

More faulty logic by AMD fanboys. Which is it ? A budget bang for your buck rig,H55/Clarksdale=200 dollarsor890FX ($160.00 MIN)+ 555=260, all so you can buy another cpu, next year, that does not exist yet ?and 890fx, you HAVE to buy a DISCRETE graphics card now.

AMD will love you , if you invest in all of this hardware , with plans to buy more, lol.

notty22I don't know if this is ROFL or just sad ? Try reading the article. Your embarrassing yourself.More faulty logic by AMD fanboys. Which is it ? A budget bang for your buck rig,H55/Clarksdale=200 dollarsor890FX ($160.00 MIN)+ 555=260, all so you can buy another cpu, next year, that does not exist yet ?and 890fx, you HAVE to buy a DISCRETE graphics card now.AMD will love you , if you invest in all of this hardware , with plans to buy more, lol.

Hmmmm, talk about embarrassing yourself - didn't you even bother to find out if your numbers were right before posting? You can get a 890FX for $140, not $160 MIN as you stated. For $155 you can get one with USB 3.0 and SATA 6Gbps, and it's not implemented with the compromises inherent with the LGA 1156 platform.

You're quite incorrect about needing a discreet GPU. AMD sells the 890GX, 790GX, 785G, 760G, and 880G. In fact, the platform they used had an integrated GPU. The nice thing with the AMD platform is, they have sideport memory, so you don't degrade CPU performance when you use the IGP due to memory contention.

So, I can get the AMD platform with motherboards around $60 with an IGP, or I can get a powerful platform with two real PCI-E 16x slots, USB 3.0, and SATA 6.0 Gbps for $155. You don't have the same choices with the Pentium G6950 platform in either direction. AM3 processors have a very diverse selection of platform.

Very interesting article.C00lit's point about businesses not overclocking is good, although I'm not sure strictly business users come to Tom's for guidance.I think these are both lab chips; maybe fun to test and tweak and play with, but far from the most sensible choice for real use. The AMD X3 chips look like fairly definitive bang for buck winners all around.

ubercakeYou know they do this all the time... When they start comparing the game performance, they drop the i5 from the comparison charts. WHY??????

I mention this in the article. The new graphics drivers really changed the game results compared to the old ones, and we don't have the i5 system here to retest. Since the game results weren't comparable anymore we left the i5 numbers out of gaming results.

lashtonI dont understand they talk about the dormant cores and you may not be successful, this is a dual core shoot out, so you intended buying a dual core, why not get the phenom II 555 and see if the cores unlock if they dont well no biggie still a fast CPU but if they do BONUS, also they dont tell you that with 2 cores the phenom can easily get OVER 4GHZ, this is typical of toms not putting everything into the tests, definately Intel fans

I don't quite follow your logic. Are you being sarcastic? They did try to unlock the cores and they were successful. bonus. They also did get two CPU cores to 4+ GHz...So they did put everything into the test that you are accusing them of not putting into the test...

My take on the drop of i5 is that their numbers for i5 were based on systems using older drivers, and there was not enough time to re-run them all with updated drivers. I have no complaints about this; I don't think any rational individual was expecting this to be a be-all, end-all article on CPU performance. I5 was not one of the CPUs being compared anyway, and confounding the results with multiple driver versions would just bring out the more trolls.

My only disagreement was with the final word, "At the end of the day, both of these CPUs offer solid value." No, they don't; not when there are clearly better bang/buck choices available from both AMD and Intel.

jtt283My take on the drop of i5 is that their numbers for i5 were based on systems using older drivers, and there was not enough time to re-run them all with updated drivers. I have no complaints about this; I don't think any rational individual was expecting this to be a be-all, end-all article on CPU performance. I5 was not one of the CPUs being compared anyway, and confounding the results with multiple driver versions would just bring out the more trolls.

I agree with you about the i5, but I do think article comparing the i3, Pentium, Athlon II x2 260, and Pentium G6950 would be kind of informative.

As much as people like to see expensive processors, the reality is that the lower end processors are often what people buy. In particular, I think the i3 is probably worth the extra money, considering it not only gets you 1 MB cache, but also hyper-threading which can be useful.

Also, I saw a review on another site on the Athlon II x2 260, which, when compared to the 255, is much faster than it should be. Performance went up more than the clock speed, and when I questioned them why, they brushed it off and just said they were only aware it was a faster clock speed. Maybe they tested wrong, maybe there is no difference, but another review showed the difference between the 260 and the Phenom II 255 to be quite small as well.

I think a lot people would be curious about matching low-end platforms on a cost basis. For example, if I save $25 on the processor, and spend it on the video card, what do the results look like. I would be impossible to do in one article, but I think a series of articles would be very interesting, covering different price points. It's time consuming, but, I think it's got broad interest and would get page hits. Of course, I could be wrong.

If you are only going to drop $200 for a CPU/Motherboard, you you really think that there are many users that are going to drop $300 for a 5850? A 5770 or a GT 250 makes more sense here.

CPU temps are always suspect to me. If it is the CPU is the main source of increased power draw, then shouldn't temperature more or less be proportional to power draw? Maybe it's those gianormous AMD heat spreaders. What are the chipset temperature?